Conformational Dynamics of Hyaluronan in Solution. I. A 13C NMR Study of Oligomers.

Conformational dynamic properties of a series of hyaluronan oligomers (UA)n, with degree of polymerization n = 2−6, have been investigated through extensive NMR experiments. Dynamic parameters T1, NOEF (by gated decoupling experiments), and T2 (by line broadening experiments) on these samples have been collected and analyzed in terms of several averaging procedures aimed at discriminating the ring position in the chain and the carbon type in the ring units U and A. Trends of these parameters and changes of carbon resonance pattern as a function of the oligomer degree of polymerization n have been interpreted in terms of changes in the local dynamics of the probe in the conformational fluctuations mainly due to the soft torsional angles at the glycosidic linkages. Preliminary molecular dynamics results on two oligomers (UA)2 and (UA)4 are used to disclose the complex variations which affect the dynamic features of the oligomers, upon increasing degree of polymerization.